Field of the Invention
The present invention relates to an optical measurement probe for guiding light generated at a time of combustion to an appliance, and an optical measurement device provided with the same, and more particularly, to a plug built-in type optical measurement probe including a spark section for performing ignition by spark discharge between electrodes, and an optical measurement device provided with the same.
Description of the Related Art
For example, at the time of evaluating the combustion state in a combustion chamber of an internal combustion engine of a car, measurement is performed using an optical measurement probe for guiding light generated at the time of combustion to an appliance (for example, see JP-A-2012-118080, and JP-A-2011-241753). As an example of such an optical measurement probe, a plug built-in type optical measurement probe including a spark section for performing ignition by spark discharge between electrodes has been known (for example, see JP-A-2006-292524).
As illustrated in FIG. 1 of JP-A-2006-292524, in a plug built-in type optical measurement probe, a light receiving section structured by an optical element or the like is held by a plug main body (an insulator section) together with the spark section. Light generated in a combustion chamber at the time of combustion by spark discharge of the spark section enters from an incidence surface of the light receiving section, and is guided to an appliance by a light guide formed of an optical fiber, for example.
Due to design restrictions based on standards, the shape of the plug main body cannot be made too large. Accordingly, in the case of integrally holding the light receiving section and the spark section by the plug main body, the light receiving section and the spark section have to be held relatively close to each other, as illustrated in FIG. 1 of JP-A-2006-292524.